1. Field of the Invention
The present invention relates to an electronic controller which includes electronic components mounted on an electronic circuit board housed within a casing.
2. Description of the Related Art
An electronic controller, which is used for controlling a vehicle or the like, includes an electronic circuit board, a plurality of electronic components, and a casing. On the electronic circuit board, connectors for electrical connection to the exterior are provided. The plurality of electronic components are mounted on the electronic circuit board. The casing is made of a resin or a metal. The electronic circuit board is housed in the casing for protection of the electronic components.
Among various types of electronic controller, an electronic controller provided in an engine room or directly mounted on an engine has a water-proof structure in view of a possibility of getting wet with water. As an example of the electronic controller described above, there exists an electronic controller disclosed in Japanese Patent Application Laid-open No. 2003-258454 (FIGS. 4 and 5).
The electronic controller described in Japanese Patent Application cited above has the following structure. A casing including vertically separated members, that is, a base and a cover, is used to interpose an electronic circuit board on which a connector is provided. A gap between a peripheral wall end surface of the base and a flange portion of the cover is sealed with a water-proof sealing material.
A sealing structure at surfaces, at which the base and the connector, and the cover and the connector are to be respectively jointed together, is as follows. A groove is provided on the connector. A projecting portion is provided on the cover at a position corresponding to the groove, whereas another projecting portion is provided on the base. A water-proof sealing material is provided in the groove of the connector. In this manner, the gaps between the cover and the connector and between the base and the connector are sealed.
In the electronic controller having the water-proof structure as described in Japanese Patent Application Laid-open No. 2003-258454 cited above, it is necessary to check a water-proofing property thereof by an airtightness test so as to ensure the water-proofing property after the assembly of the electronic controller.
In a case of electronic controllers using an adhesive or a liquid packing as a sealing material, when an electronic controller which does not meet a predetermined standard because of a small application amount of the sealing material is found in the airtightness test for the casing of the electronic controller, it is necessary to additionally apply the sealing material from the exterior to an area of the casing, in which a joint is to be established, and to conduct the airtightness test again.
In the case of the electronic controller described above, however, the application amount of the sealing material on the area of the casing, in which a joint is to be established, cannot be easily checked. Therefore, it is difficult to identify a portion from which air leaks, specifically, a portion which requires to be additionally applied with the sealing material.
If, for example, complicated tasks such as immersing the electronic controller into a tank storing water therein and feeding air into the electronic controller to identify the air leakage portion are performed, the air leakage portion can be identified. However, conducting such tasks in a fabrication line for the electronic controllers is not practical in view of a line space, capital investment, and fabrication cost.
As described above, the conventional electronic controllers have had a problem in that it is difficult to identify a portion with a small amount of the sealing material, which has a high possibility of air leakage, and to additionally apply the sealing material only to the identified portion at the location of assembly.
As countermeasures against the aforementioned problem, it is possible to conceive of additionally applying the sealing material over the entire periphery from the exterior of the casing of the electronic controller. In this case, however, there arises another problem in that the amount of the sealing material to be used disadvantageously increases, thereby increasing the cost of the electronic controller.